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Mad City Flyers 10-14-2015 07:58 PM

Binder Design Stealth Build
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Well we're at it again! Haven't even flown our 2.6" Mad Cow - Tomach and off we go to the next build project.....

This time the Mad City Flyers Skunk Works is building a Binder Design 4" Stealth. Found a guy selling an old kit for 1/2 price and couldn't resist.

We are thinking that this could be the rocket for an L2 cert attempt next spring. To support an L2 motor here's the upgrades we will be making to the kit:
  • Internal epoxy fillets in addition to externals
  • Replace launch lugs with 1515 Delrin Rail Buttons
  • Dual Deploy by adding the Binder Design AV bay
  • Giant Leap Rocketry motor retainer - instead of friction fit
  • Tubular nylon recovery cord - replace included elastic ribbon

The final height should be around 6 feet with the AV bay inserted and weight around 5.5 lbs. We've already got an H178-DM for first flight.

More pics to follow as we start putting it all together!

Matt and Nate

Rex R 10-14-2015 08:25 PM

hmm, are you going to MWP? if so maybe you should get about 5' of flat braided Kevlar from Tim for use from the motor mount to the forward end of the body, and a nomex chute 'hanky' to protect the nylon cord + chute.

Mad City Flyers 10-14-2015 08:48 PM

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Hi Rex,

Yes we are planning to fly the 2.6" FG Tomach on our I-357 at MWP on Sunday.

Tim's trailer is dangerous as it has all the goodies and the incentive of no shipping charges.... this leads to overspending my allowance.

We have been adding Nome parachute protectors to all of our Mid and High power rockets in addition to a handful of dog barf.

We have a Giant Leap Rocketry Fireball that we might just insert in the booster to minimize the chances of a zipper.

We will also CA coat the inner cardboard tube ends to add strength.

Got the fins all sanded (100, 150, 220, 320 grit) and they are smooth as glass.

The booster tube comes marked with lines for the fin slots and the lug/rail buttons. After very careful marking of the fin slots using a T square we got the slots cut out.

We'll get the motor mount built next.

BTW, we thought your PVC launch pad was quite nice and did a great job!


Matt and Nate

MadHatter 10-15-2015 07:46 AM

15/15 rail guides are required if your rocket weighs more than 50 pounds, unless you are planning to put a lot of weight in the nose cone you will want to use 10/10 guides.

Mad City Flyers 10-15-2015 12:17 PM

Good to know! If there is no benefit we'll use the 1010 rail buttons. Appreciate the guidance.


Mad City Flyers 10-16-2015 06:36 PM

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Made some progress over the past couple of days:
  • Binder Design AV bay kit arrived. It includes some nice goodies such as the drogue chute, 18' of nylon recovery cord, and a switch to be externally mounted.
  • Changed plan to 1010 rail buttons which I support with T nuts anchored in plywood. I sand down all the rough edges on the plywood anchors to make sure the recovery laundry doesn't hang up.
  • Used some 4" tube to create an extension from the nose cone that will allow for a bulk head and anchor for the recovery harness connected to the main parachute. You can see from the dry fit picture that the total height is now over 6 feet and makes our favorite MDRM look puny.

This weekend should provide some time for CA coating of the tube ends and motor mount assembly.


Matt and Nate

Mad City Flyers 10-18-2015 08:06 PM

Love hate relationship with 6 minute epoxy
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Only 1 soccer game this weekend so we made some more progress on the Stealth. We used the Great Planes 6 minutes epoxy. I think our resin was a little old as it set up in more like 2 minutes, which made for a race to get all the pieces we were attaching set properly.
  • Attached the bulkhead plates together after lots of sanding to make sure they fit smoothly in the payload and booster sections.
  • Built the AV bay sled using plywood, aluminum tubing, and JB Weld epoxy to hold the aluminum to the plywood. Let it set up overnight with a weight on it.
  • Motor mount forward centering ring set and then the motor tube was fixed to the booster. We did not epoxy the aft centering ring so we can set internal fillets.
  • Applied 6 minute epoxy to the fin tabs and set them in place against the motor mount using the fin guide (paper with llines on it) provided with the kit. This worked fin although the rapidly setting epoxy made for a lot of excitement as Nate and I tried to fit the fins through the tab holes and then hold them straight.

Because we chose to convert the rocket to dual deploy we had a bit of a build challenge with the payload section, nose cone and bulkhead. The original design has the nose cone friction fit (or glued) to the payload section and then a standard bulkhead and anchor eyebolt is provided for the recovery cord/parachute.

The AV bay prevents the placement of the bulkhead in the payload section so we fortunately had some extra 4" heavy wall body tube to create a small 4" extension from the nose cone. We then placed the bulkhead in the body with the eyebolt. So our Stealth is now over 6' with the addition of the AV bay and extension of the nose cone.

On to fin fillets-----

Cheers all,

Matt and Nate

Mad City Flyers 11-26-2015 01:49 PM

Fillets and more fillets
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Managed to get a little more work done on the Stealth:
  • payload bay canards are in and internal fillets set
  • internal fillets on canards
  • booster fin internal fillets done
  • booster external fillets started

We are still very happy with the method of creating external fillets that uses the following formula:
  • 7.5 ml Great Planes 30min Epoxy Resin
  • 7.5 ml Great Planes 30 min Epoxy Hardner
  • 1 full teaspoon FGCI Phenolic Microballons
  • 1 full teaspoon West System 403 Microfibers

We mix the resin and harder first, then the microfibers, then the micro balloons. The resulting maroon paste is very easy to work with and sets up nicely. To date we have never seen a fracture line in any of the fillets we've set with this mixture.

To create the very smooth and even initial epoxy set we soak a short piece of 1"PVC in rubbing alcohol and slowly drag it through the groove between the fin and body wall. You have to be ready to wipe up the extra epoxy that oozes out the back.

After set up its lots of sanding and then filling the gaps with wood filler.

Plan for this beast is our L2 certification on a J425R!!!

Should get the AV bay built over the Xmas break.

Cheers all,

Matt and Nate

Mad City Flyers 01-26-2016 07:19 PM

AV Bay Complete
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Well Christmas was wonderful as Santa brought a StratoLogger CF for the AV bay and I had a little time off to work on the Stealth.

The Binder AV bay is 14" long so there is plenty of room to comfortably fit the altimeter, battery, and wiring for the switch. I debated installing a secondary altimeter as there is plenty of room on the sled, but don't feel it's necessary. This was be a level 2 rocket max and it will have motor eject for the drogue as a back up.

We chose the Dog House rocketry charge wells that have electrical connections running through the anchor bolts. This is a nice feature as you don't have to install a connector block on the cap.

The Binder AV bay included a screw type switch that seems to work easy enough.

Now have to wait for spring to test the ejection charges!

Happy New Year!

Matt and Nate

Mad City Flyers 01-26-2016 07:33 PM

Fillets the never ending story....
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Last year Nate and I built an NCR SA-14 Archer, which we love and have enjoyed flying on everything from a G80 to an H195. This rocket of course has 4 fins and 4 canards that run nearly the full length of the booster. You would have thought we'd learned our lesson about how much work creating nice fillets can be when you have to do 16 of them....

Well enough whining......found time to get sanding (150 - 320 grit) on the epoxy fillets and then fill with the color changing Elmers wood filler. More sanding (150-320 grit) and the Stealth is now ready for its first coat of primer.

Once we hit about 50 degrees outside we will start painting.. looks like we are waiting until March.

Gives me time to study for the L2 exam!

Stay warm!


Matt and Nate

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